1. Field of the Invention
The field of the invention generally relates to apparatuses having both large-feature-size components and small-feature-size components, and methods of making such apparatuses. The invention more particularly relates to combination of VLSI integrated circuits and macro-scale components to form a single device.
2. Description of the Related Art
VLSI provides many effective methods for creation of microscopic-scale and smaller components. Such miniaturization provides many advantages in terms of speed of operation, size of footprint, amount of necessary resources, and speed of manufacture for electronic devices.
Unfortunately, some components of electronic devices are not well-suited to formation through well-known VLSI processes. These components often are necessarily very large (macroscopic-scale) relative to devices or components of devices formed through VLSI. One such component is an antenna, which may need to have a characteristic length to allow for adequate transmission on a preferred frequency, and for which the characteristic length in question may be appropriately measured in centimeters or meters, for example. Formation of a conductor for use as an antenna using VLSI tends to waste time and material resources, as a 30 cm conductor (for example) can easily be formed through less expensive processes.
Thus, the problem then becomes a matter of combining a large-scale component such as an antenna with a small-scale component such as an integrated circuit. For a conventional radio, this may involve use of packaging for the integrated circuit, conductors on a printed circuit board, a connector attached to the printed circuit board, and an antenna attached to the connector. This approach is simple enough for a device having rigid packaging and flexible size constraints. However, other applications may have more demanding requirements for size and materials cost.
In particular, it may be useful to have a small radio-transmitter with flexible materials allowing for bending and other abusive actions without degradation in functionality. Similarly, such a small radio-transmitter may need to be producible rapidly in quantities of millions or billions, thus requiring ease of assembly and relatively inexpensive materials on a per-unit basis. Using a printed-circuit board approach for such a radio-transmitter will likely not succeed. Moreover, avoiding such time (and/or space) consuming processing operations as thermal cure may be advantageous.
It is possible to separately produce elements, such as integrated circuits and then place them where desired on a different and perhaps larger substrate. Prior techniques can be generally divided into two types: deterministic methods or random methods. Deterministic methods, such as pick and place, use a human or robot arm to pick each element and place it into its corresponding location in a different substrate. Pick and place methods place devices generally one at a time, and are generally not applicable to very small or numerous elements such as those needed for large arrays, such as an active matrix liquid crystal display. Random placement techniques are more effective and result in high yields if the elements to be placed have the right shape. U.S. Pat. Nos. 5,545,291 and 5,904,545 describe methods that use random placement. In this method, microstructures are assembled onto a different substrate through fluid transport. This is sometimes referred to as fluidic self assembly (FSA). Using this technique, various integrated circuits, each containing a functional component, may be fabricated on one substrate and then separated from that substrate and assembled onto a separate substrate through the fluidic self assembly process. The process involves combining the integrated circuits with a fluid, and dispensing the fluid and integrated circuits over the surface of a receiving substrate that has receptor regions or openings. The integrated circuits flow in the fluid over the surface and randomly align into receptor regions, thereby becoming embedded in the substrate.
Once the integrated circuits have been deposited into the receptor regions, the remainder of the device can be assembled. Typically, this involves coating the substrate with a planarization layer to provide electrical insulation and physical retention for the integrated circuits. The planarization layer creates a level surface on top of the substrate by filling in the portions of the receptor regions that are not filled by integrated circuits. After the planarization layer has been deposited, other elements, including pixel electrodes and traces for example, may be installed.
Using FSA, the functional components of the device can be manufactured and tested separately from the rest of the device.